U.S. patent application number 10/327295 was filed with the patent office on 2003-05-08 for altitude simulator for dynamometer testing.
This patent application is currently assigned to DELPHI TECHNOLOGIES, INC.. Invention is credited to Maloney, Peter James, Osterhout, Matt, Smith, James Craig.
Application Number | 20030084712 10/327295 |
Document ID | / |
Family ID | 24787312 |
Filed Date | 2003-05-08 |
United States Patent
Application |
20030084712 |
Kind Code |
A1 |
Smith, James Craig ; et
al. |
May 8, 2003 |
Altitude simulator for dynamometer testing
Abstract
A method and apparatus for conducting dynamometric testing of an
internal combustion engine at a test site under a simulated
atmospheric pressure that differs substantially from an actual
ambient atmospheric pressure existing at the test site. The
internal combustion engine has an air inlet for supplying an intake
airflow for combustion within the internal combustion engine and an
exhaust outlet for exhausting an exhaust flow exiting from the
internal combustion engine. The method includes the steps of
subjecting the air inlet to the simulated atmospheric pressure,
subjecting the exhaust outlet to the simulated atmospheric pressure
and operating the internal combustion engine while both of the air
inlet and the exhaust outlet are subjected to the simulated
atmospheric pressure. The apparatus includes an exhaust pressure
controller for maintaining the exhaust outlet of the internal
combustion engine substantially equal to a determined exhaust
pressure during operation of the internal combustion engine and an
intake pressure controller for maintaining the air inlet of the
internal combustion engine substantially equal to a determined
intake pressure during operation of the internal combustion
engine.
Inventors: |
Smith, James Craig;
(Farmington Hills, MI) ; Maloney, Peter James;
(New Hudson, MI) ; Osterhout, Matt; (Northstreet,
MI) |
Correspondence
Address: |
VINCENT A. CICHOSZ
DELPHI TECHNOLOGIES, INC.
P.O. Box 5052
Mail Code: 480-410-202
Troy
MI
48007-5052
US
|
Assignee: |
DELPHI TECHNOLOGIES, INC.
|
Family ID: |
24787312 |
Appl. No.: |
10/327295 |
Filed: |
December 20, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10327295 |
Dec 20, 2002 |
|
|
|
09694078 |
Oct 20, 2000 |
|
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Current U.S.
Class: |
73/116.05 ;
73/118.02 |
Current CPC
Class: |
F01N 11/00 20130101;
G01M 15/02 20130101; G01M 15/00 20130101 |
Class at
Publication: |
73/118.1 |
International
Class: |
G01M 019/00 |
Claims
What is claimed is:
1. An apparatus for use in conjunction with performing dynamometric
procedures on an internal combustion engine residing in an ambient
pressure environment, said engine having an air inlet and an
exhaust outlet comprising: a pressure control means coupled to the
air inlet and the exhaust outlet for controlling pressure
conditions at the air inlet and the exhaust outlet independent of
the ambient pressure environment; said pressure control means
effective to isolate the air inlet and exhaust outlet from said
ambient pressure environment.
2. An apparatus for use in conjunction with performing dynamometric
procedures on an internal combustion engine residing in an ambient
pressure environment, said engine having an air inlet and an
exhaust outlet comprising: a first pressure control means coupled
to the air inlet for controlling pressure conditions at the air
inlet independent of the ambient pressure environment; a second
pressure control means coupled to the exhaust outlet for
controlling pressure conditions at the exhaust outlet independent
of the ambient pressure environment; said first and second pressure
control means effective to isolate the air inlet and exhaust outlet
from said ambient pressure environment.
3. The apparatus in claim 2, wherein the first pressure control
means coupled to the inlet comprises an intake pressure controller,
a pressure transducer, and a choke valve; wherein the intake
pressure controller is operable to control the choke valve based
upon input from the pressure transducer.
4. The apparatus in claim 2, wherein the second pressure control
means coupled to the exhaust outlet comprises an exhaust pump, a
control valve, a pressure sensor and a controller, wherein the
controller is operable to control the control valve, based upon
input from the pressure sensor.
5. The apparatus in claim 4, wherein the controller is operable to
control the exhaust pump.
6. The apparatus in claim 4, wherein the second pressure control
means further comprises a flow accumulation device.
7. The apparatus in claim 3, wherein the first pressure control
means further comprises a flow accumulation device.
8. The apparatus in claim 3, wherein the first pressure control
means further comprises an air conditioning unit for supplying
conditioned air flow to the engine.
Description
FIELD OF THE INVENTION
[0001] The present invention generally relates to a method and
apparatus used to test the operational performance (i.e., for
dynamometric testing) of an internal combustion engine under
various ambient atmospheric pressures, thereby simulating operation
of the engine at various altitudes. More particularly, the
invention pertains to a method and apparatus that allow
dynamometric testing of an internal combustion engine at various
ambient atmospheric pressures, without requiring that the entire
engine be enclosed within a barometric chamber of controlled
pressure.
BACKGROUND OF THE INVENTION
[0002] The following background information is provided to assist
the reader in understanding the invention described and claimed
herein. Accordingly, any terms used herein are not intended to be
limited to any particular narrow interpretation, unless
specifically so indicated.
[0003] The manufacturers of modern vehicles powered by an internal
combustion engine subject the vehicles to various testing
procedures. One such testing procedure that is typically performed
is "dynamometric testing", which involves running the engine under
actual or simulated likely-to-be encountered conditions, while
simultaneously testing and measuring various parameters.
[0004] In one sense, an internal combustion engine can be viewed as
an air pump that also produces rotational power. Accordingly, the
characteristics and performance of an internal combustion engine
can be significantly altered by a change in the ambient atmospheric
pressure at which the engine is operated. For example, according to
Boyle's Law, air density varies directly with respect to
atmospheric pressure and inversely with respect to atmospheric
temperature, i.e., .rho.(air density)=P/RT. Whereas a typical
ambient atmospheric pressure at sea level is on the order of 100
kPa (i.e., kilopascals), a typical ambient atmospheric pressure in
the location of Denver, Colo., U.S.A. is typically on the order of
80 kPa, or about 20% less that at sea level. With other factors
remaining equal (e.g., ambient temperature and humidity), this
results in an engine "at altitude" (e.g., in Denver) receiving a
20% less charge of oxygen with each intake stroke, given the same
engine speed, throttle angle, EGR percentage, etc. Additionally,
the internal combustion engines of most modern vehicles adjust,
usually by software, the fuel delivery based on the ambient
atmospheric pressure, sometimes directly measured, but usually
estimated from other measured parameters. Accordingly, at altitude,
the maximum power output of the engine can be significantly
reduced.
[0005] Increasingly, the operation of a modern internal combustion
engine vehicle is controlled by microprocessor software. Apart from
the reduced maximum power output at altitude, there are a
substantial number of factors in the vehicle's software that are
influenced by the ambient atmospheric pressure. For all of these
reasons, it has been customary for vehicle manufacturers to
dynamometrically (i.e., operationally) test their engines under
conditions of varying atmospheric pressure. One manner in which
vehicles have been traditionally tested under reduced atmospheric
pressures is to actually operate the vehicles at altitude, e.g., in
Denver, up Pike's Peak, etc. For more preliminary testing,
manufacturers have also used so-called "dynamometric chambers".
[0006] Such dynamometric chambers are closed barometric cells in
which a lower than ambient pressure can be maintained. The engine
is dynamometrically tested (run under various operating loads,
conditions, etc.) within the chamber.
[0007] However, such dynamometric chambers can be expensive to
build, operate and maintain. Since a rather large pressure
differential must be maintained across the boundaries of the
pressure cell, a dynamometric chamber is similar to a diving bell,
requiring substantial and expensive structural support.
OBJECTIVES OF THE INVENTION
[0008] Accordingly, one objective of the present invention is the
provision of a method and apparatus for the dynamometric testing of
an internal combustion engine under varying ambient atmospheric
pressures without requiring the building, operation or maintenance
of a cumbersome and expensive barometric cell.
[0009] Another objective of the invention is the provision of a
method and apparatus for the dynamometric testing of an internal
combustion engine under varying ambient atmospheric pressures that
is relatively inexpensive in construction and reliable in
operation.
[0010] Yet another objective of the present invention is the
provision of a method and apparatus for the dynamometric testing of
an internal combustion engine under varying ambient atmospheric
pressures which is, on the whole, safer than previously used
barometric chambers, since pressures are controlled only across the
inlet and output interfaces of the engine system, as opposed to
over the entire surface of a dynamometric chamber. Therefore, the
overall pressure-induced forces acting on the control surfaces are
considerably reduced.
[0011] In addition to the objectives and advantages listed above,
various other objectives and advantages of the invention will
become more readily apparent to persons skilled in the relevant art
from a reading of the detailed description section of this
document. The other objectives and advantages will become
particularly apparent when the detailed description is considered
along with the drawings and claims presented herein.
SUMMARY OF THE INVENTION
[0012] The foregoing objectives and advantages are attained by the
various embodiments of the invention summarized below.
[0013] In one aspect, the invention generally features a method for
conducting dynamometric testing of an internal combustion engine at
a test site under a simulated atmospheric pressure that differs
substantially from an actual ambient atmospheric pressure existing
at the test site. The internal combustion engine has an air inlet
for supplying an intake airflow for combustion within the internal
combustion engine and an exhaust outlet for exhausting an exhaust
flow exiting from the internal combustion engine. The method
includes the steps of subjecting the air inlet to the simulated
atmospheric pressure, subjecting the exhaust outlet to the
simulated atmospheric pressure and operating the internal
combustion engine while both of the air inlet and the exhaust
outlet are subjected to the simulated atmospheric pressure.
[0014] In another aspect, the invention generally features an
altitude simulator for dynamometer testing for conducting
dynamometric testing of an internal combustion engine at a test
site under a simulated atmospheric pressure that differs
substantially from an actual ambient atmospheric pressure existing
at the test site. The internal combustion engine has an air inlet
for supplying an intake airflow for combustion within the internal
combustion engine and an exhaust outlet for exhausting an exhaust
flow exiting from the internal combustion engine. The altitude
simulator for dynamometer testing includes an exhaust pressure
controller for maintaining the exhaust outlet of the internal
combustion engine substantially equal to a determined exhaust
pressure during operation of the internal combustion engine and an
intake pressure controller for maintaining the air inlet of the
internal combustion engine substantially equal to a determined
intake pressure during operation of the internal combustion
engine.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is an overall diagrammatic view of an altitude
simulator for dynamometer testing constructed according to the
invention.
[0016] FIG. 2 is a diagrammatic view of an exhaust pressure
controller unit of the altitude simulator for dynamometer testing
of FIG. 1.
[0017] FIG. 3 is a diagrammatic view of an air intake pressure
controller of the altitude simulator for dynamometer testing of
FIG. 1.
[0018] FIG. 4 is a diagrammatic view of an air conditioning unit
used in the air intake pressure controller of FIG. 3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] Referring initially to FIG. 1, an altitude simulator for
dynamometer testing, constructed according to the present
invention, is generally indicated by reference numeral 10. The
altitude simulator 10 is, in FIG. 1, shown connected to an internal
combustion engine system 12, which includes an internal combustion
engine 14, an air intake system 16 for supplying the engine system
12 with a flow of air for supporting the combustion of fuel
therein, and an exhaust system 18 for exhausting the products of
combustion therefrom. Commonly, the air intake system 16 will
include such components as an air cleaner/filter, a carburetion
system, an intake manifold, etc. Typically, the exhaust system 18
will include such components as an exhaust manifold, a catalytic
converter unit, and various exhaust pipes and connections
terminating in a tailpipe 20.
[0020] In contrast to the previously utilized dynamometric chamber
approach to altitude simulation, the present invention recognizes
that, since the only parts of an internal combustion engine that
are affected by barometric pressure are the air inlet and the
exhaust outlet of the engine, only these relatively small volumes
need be pressure controlled in order to subject the operational
characteristics of the engine as a whole to changes in ambient
pressure (thereby simulating changes in altitude).
[0021] The altitude simulator 10 itself generally includes a
exhaust pressure controller 22 and an intake pressure controller
24, each of which is shown in more detail in FIGS. 2 and 3,
respectively, and described more fully below.
[0022] In FIG. 1, the intake pressure controller 24 is shown as
being connected upstream of the air intake system 16, and the
exhaust pressure controller 22 is shown as being connected
downstream of the tailpipe 20. It will be understood by those of
ordinary skill in the art that the precise points at which the air
intake pressure controller 24 and the exhaust pressure controller
22 are connected to the engine system 12 are not of primary
concern. The primary consideration is rather that the air inlet
through which intake air is introduced into the engine system 12
and the exhaust outlet and through which exhaust gases are
exhausted from the engine system 12 be maintained at the desired
pressure.
[0023] Referring now to FIG. 2, the exhaust pressure controller 22
includes an exhaust pump 26, which is connected to the exhaust
outlet of the engine system 12. In the presently preferred
embodiment, as shown in FIGS. 1 and 2, the exhaust pump 26 is
connected to the tailpipe 20, which functions as the exhaust outlet
of the engine system 12. The exhaust pump 26 is chosen to have a
capacity (i.e., in cubic feet per minute, etc.) sufficient to
produce an absolute pressure at the exhaust outlet (e.g., the
tailpipe 20) of the engine system 12 which is at least as low as,
and preferably lower than, the absolute pressure at which the
dynamometric testing is to be carried out, during such time as the
engine system 12 is running, and over the entire range of operation
of the engine system 12. For example, as noted above, an absolute
pressure of 80 kPa is typically used for dynamometric testing to
represent a common absolute ambient atmospheric pressure likely to
be encountered in Denver, Colo. Assuming that the actual
atmospheric pressure at the testing site is on the order of 100
kPa, then the capacity of the exhaust pump 26 must be sufficient to
pull at least a negative pressure of 20 kPa, in order to reach the
desired 80 kPa representative of the Denver, Colo. ambient
atmospheric pressure. Additionally, the exhaust pump 26 must be of
sufficient capacity to maintain this negative pressure differential
(e.g., 20 kPa) throughout the entire operating range over which the
engine system 12 is tested. For example, maintaining a given
negative pressure differential (e.g., 20 kPa) will require a
greater flow capacity for exhaust pump 26 if the tested operating
range of the engine system 12 is to include operation at full
throttle (i.e., with the throttle wide open) as opposed to
operation only at lower engine speeds and light loads.
[0024] In actual operational tests, a diesel particulate exhaust
pump has been employed for the exhaust pump 26. Such a diesel
particulate exhaust pump is used in the testing of diesel engines
and, since it is utilized to maintain the particulate matter
produced by diesel engines (e.g., soot) airborne, a diesel
particulate exhaust pump has a substantially high flow capacity and
the ability to pull a substantial negative pressure. It is
estimated, for example, that such a diesel particulate pump was
able to pull a negative pressure of 25 kPa over the entire
dynamometrically tested range of a typical 4-cylinder passenger
vehicle engine.
[0025] The exhaust pump 26 is connected to exhaust the effluent
from the exhaust outlet of the internal combustion engine system 12
(i.e., the tailpipe 20) and therefore, in effect, creates a
barometric control surface 28 at the terminus of the exhaust outlet
of the internal combustion engine system 12 (i.e., at the endpoint
of the tailpipe 20). In the present invention, the barometric
control surface 28 extends only over the exhaust outlet of the
internal combustion engine 12. This is in contrast to the prior art
approaches, wherein a barometric control surface extending over the
entire engine had to be established and maintained. Since the
exhaust pump 26, as explained above, will pull a higher than
desired negative pressure throughout the range of testing, air at
the ambient atmospheric pressure is admitted from the test site to
raise the pressure at the barometric control surface 28 (i.e., the
outlet of the tailpipe 20) to the desired simulated atmospheric
pressure. To this end, the exhaust pressure controller 22 includes
an inlet valve 30 for admitting air at ambient atmospheric pressure
from the test site to a point which is preferably located
substantially adjacent the barometric control surface 28. The
opening and closing of the inlet valve 30 is controlled by a
Feedback and Feed Forward Controller 32, which is preferably
provided in the form of a numerical processor, such as, for
example, a microprocessor. The Feedback and Feed Forward Controller
32 is provided with a variable input of the "Commanded Tailpipe
Pressure" and also receives a data signal indicative of the
absolute pressure existing at the barometric control surface,
namely, P.sub.Tailpipe which is generated by an absolute pressure
sensor 34 positioned preferably to read the pressure at a point
substantially adjacent the barometric control surface 28. If
P.sub.Tailpipe is less than the Commanded Tailpipe Pressure, the
Feedback and Feed Forward Controller 32 controls the inlet valve 30
so as to admit ambient air from the test site to a point
substantially adjacent the barometric control surface 28 and
thereby raise the pressure at the barometric control surface 28 to
the desired level.
[0026] The Feedback and Feed Forward Controller 32 controls the
inlet valve 30 through a valve actuator 36. Preferably, the valve
actuator 36 includes a failsafe driver 38. Such valve actuators
incorporating a failsafe driver are available commercially and are
well known to those of ordinary skill in the art in the field of
the invention. The failsafe driver 38 may be built into the valve
actuator 36 but can be a standalone device.
[0027] The failsafe driver 38 is, in fact, a controller for the
valve actuator 36. The failsafe driver 38 can be programmed to act
as a simple (or local) feedback controller for the valve actuator
36 and can also accommodate external commands to drive the valve
actuator 36 through this local controller. The failsafe driver 38
can produce a 2-10 mA signal that is typical of such industrial
applications. The 2-10 mA signal commands the valve actuator 36,
which in turn positions the larger intake valve 30.
[0028] The Feedback and Feed Forward Controller 32 may optionally
be furnished with additional variable input signals, including
"Engine Mass Rate Out", "P.sub.Ambient" and "T.sub.Ambient". As is
well understood in the field, the inclusion of these additional
variables allows the engine intake mass rate to be calculated. By
using this additional information, the feed forward section of the
Feedback and Feed Forward Controller 32 can be made more effective.
This is most useful for dynamic testing, where the speed and the
loading conditions of the engine system 12 are changing during
testing. In steady state testing, use of these additional variables
is not critical. Use of the additional variables Engine Mass Rate
Out, P.sub.Ambient and T.sub.Ambient allows the control command to
be instantly changed when the operating conditions of the engine
system 12 change, using feed forward on these variables, together
with a dynamic physical model of the system at hand. This is in
contrast to using just feedback and having to wait for control
errors to arise before the control command is changed. This feed
forward approach is important in non-linear applications and in
applications that can vary over a wide range of such
non-linearities, which is the case of an engine's air intake over
the span of normal operating conditions.
[0029] Referring now most particularly to FIG. 3, the intake
pressure controller 24 includes an air conditioning unit 40,
described more fully below in connection with FIG. 4, which
supplies a sufficient flow of conditioned air at a predetermined
pressure, humidity and temperature to exceed what the engine system
12 might consume at the upper limit of dynamometric testing. In
order to reduce the pressure at which this conditioned air is
supplied to the engine system 12, a choke valve 42 is positioned
downstream of the air conditioning unit 40 and upstream of the air
inlet of the engine system 12. Whereas, in the exhaust pressure
controller 22, the exhaust pump 26 is employed to draw down the
pressure to below the ambient pressure existing at the test site,
here, the engine system 12 itself acts as an air pump. The choke
valve 42 positioned between the air conditioning unit 40 and the
air inlet of the engine system 12 provides a resistance against
which the engine system 12 can produce the required pressure
drop.
[0030] The degree of closure of the choke valve 42 is controlled by
a first pressure controller 44, which is also preferably provided
in the form of a numerical processor (e.g., a microprocessor). The
first pressure controller 44 is provided with a Desired Intake
Pressure variable and a signal generated by a pressure transducer
46. The pressure transducer 46 is preferably mounted just upstream
of the air inlet of the engine system 12 (e.g., just ahead of the
air cleaner thereof). The first pressure controller 44 manipulates
the choke valve 42 (through an actuator 48 associated with the
choke valve 42) so as to maintain the pressure registered by the
pressure transducer 46 within acceptable limits of the Desired
Intake Pressure.
[0031] Another barometric control surface 49 is established at the
intake system 16 of the engine system 12. Again, in contrast to the
prior art approach, the barometric control surface 49 extends only
over the air inlet of the engine system 12 and not over the entire
extent of the engine system 12.
[0032] The effectiveness of the choke valve 42 is increased if the
pressure drop across the choke valve 42 is maintained within a
certain range. If the pressure differential across the choke valve
42 is too small, the choke valve 42 becomes, to some degree,
ineffective. If, on the other hand, the pressure differential
across the choke valve 42 is too great, the choke valve 42 becomes
too sensitive, in that small changes in the configuration of the
choke valve 42 produce very large changes in downstream pressure.
Accordingly, in order to maintain the pressure just upstream of the
choke valve 42 within this desired range, the intake pressure
controller 24 is preferably provided with a pressure dump mechanism
50, which generally includes a dump valve 52, an actuator 54 for
actuating the dump valve 52, a second pressure controller 56 and a
differential pressure transducer 58, which is mounted across the
choke valve 42. The second pressure controller 56 receives a signal
from the differential pressure transducer 58 indicating the
pressure existing across the choke valve 42 and signals the
actuator 54 to actuate the dump valve 52 so as to maintain this
pressure within a range wherein, preferably, the effectiveness of
the choke valve 42 will be maximized. Provision of the pressure
dump mechanism 50 additionally prevents the ductwork connecting the
air conditioning unit 40 to the remainder of the system from being
exposed to excessive pressure forces.
[0033] Referring primarily now to FIG. 4, the air conditioning unit
40, shown there in more detail, generally includes a dryer stage 60
for dehumidifying the air intake into the unit, a conditioned air
supply stage 62 for adjusting the temperature and humidity of the
air and a final electronic pressure control stage 64. Air
conditioning units such as are shown in FIGS. 3 and 4 and which are
used in the practice of the present invention are available as off
the shelf units from commercial vendors, as is well understood by
the average artisans in the field to which the present invention
pertains.
[0034] The Feedback and Feed Forward Controller 32 of FIG. 2 and
the first and second pressure controllers 44 and 54, respectively,
of FIG. 3 may be all be implemented within a single microprocessor
configuration, or the different controllers can be each implemented
within a separate microprocessor, as desired.
[0035] While the present invention has been disclosed by way of a
description of a particularly preferred embodiment or a number of
particularly preferred embodiments, it will be readily apparent to
those of ordinary skill in the art that various substitutions of
equivalents can be effected without departing from either the
spirit or scope of the invention as set forth in the appended
claims.
* * * * *